1. Field of the Invention
The present invention relates to a stereo camera that captures images for stereo vision.
2. Description of the Related Art
Stereo vision utilizing a pair of perspective images of a subject is well known. A stereo camera takes a pair of perspective images (commonly referred to as parallax images) from different viewpoints, which correspond to the right and left eye, thereby binocular vision is emulated because of the parallax between the two images. For a stereo camera, a twin lens system or a single lens system is known. A stereo camera with a twin lens system obtains each parallax image individually through two independent photographing systems. A camera with a single lens system bifurcates the light path of the photographing lens system by using a mirror or a prism, so that the right and left parallax images are obtained by the single imaging device mounted in the camera.
In the stereo-image capturing operation, convergence between a pair of parallax images should be adjusted for natural stereo vision. The convergence of a stereo camera system is often manually adjusted. However, in Japanese unexamined patent publication (KOKAI) No. 2000-152282, a stereo camera with an automatic convergence adjusting mechanism is disclosed. In the above-disclosed stereo camera, the light path of the single lens system is bifurcated by a prism. Each branched light path is reflected toward a subject by a mirror which is rotatable about a predetermined axis and the right and left parallax images are taken in turn. The distance between the apparatus and a subject is detected by triangular surveying with a distance measurement device. The tilt of the mirrors is controlled in accordance with the distance of the subject obtained by the distance measurement device, so that the convergence is automatically adjusted.
However, the above-disclosed automatic convergence adjusting mechanism requires a distinct distance measurement device, so that it brings about a complicated construction and high cost. The above mechanism also requires space and complicated software to control the mirrors for adjusting the convergence.